Iron-deficiency in children has been reported to be associated with behavioral disturbances and an overall diminishment in intellectual performance. Given the relatively high prevalence of iron-deficiency in children and the potential contribution of this state to impaired behavioral and scholastic performance, it is imperative that the nature of the relationship between the two conditions be determined. Accordingly, the objectives of this project have as its goals to determine whether specific biochemical and neurochemical changes relating to synthesis and degradation of the biogenic amine neurotransmitters exist in children during an iron-deficient state. This will be accomplished by: 1) measuring platelet monoamine oxidase (MAO) activity (a peripheral marker for brain MAO activity) in iron-deficient and normal control children. 2) measuring urinary levels of the amine neurotransmitters and their major metabolites. 3) measuring urinary 3-methoxy-4-hydroxyphenylethylamine (a peripheral marker for brain norepinephrine turnover). Methods which will be used to measure platelet MAO and urinary amines and metabolites are established procedures described in the literature.